I’ve been getting loads of requests recently for retro-fitting disc brake mounts to older steel frames. People don’t seem quite sure what’s involved and how to go about it. The good news is that on most frames it’s a pretty simple (and cheap) process that involves brazing on a disk tab and in almost all cases, fitting a brace between the seat and chain stays. As a nice touch, it’s possible to remove the old canti bosses and put some hose type cable guides on in place of the old cable stops. Things to watch out for include:

The rotor has enough room to clear the stays. Only really a problem if using big rotors or wavey-davey stays.

If the frame has mudguard or pannier eyelets, these will probably have to come off. In fact if you want to fit panniers to a frame with discs that’s a whole other story.

I’ve put a few photos on the gallery of the last conversion I did (before paint).